Patent Literature 1 described below discloses a weld overlay (overlay welding, build-up welding) system which weld overlays the outer peripheral surface of a linear tube with a circular cross-section while rotating the tube. For example, in a case where a weld overlay material with a high corrosion resistance is applied to the outer peripheral surface of the tube with the circular cross-section, the corrosion resistance of the outer peripheral surface of the tube can be improved.